Fluorene-based π-conjugated oligomers for efficient three-photon excited photoluminescence and lasing

Article abstract of DOI:10.1002/chem.200901460

A novel series of diphenylamino- and 1,2,4-triazole-end-capped, fluorene-based, π-conjugated oligomers that includes extended oligofluorenes and oligothienylfluorenes has been synthesized by means of the palladiumcatalyzed Suzuki cross-coupling of 9,9dibu

Full text of DOI:10.1002/chem.200901460

FULL PAPER
DOI: 10.1002/chem.200901460
Fluorene-Based p-Conjugated Oligomers for Efficient Three-Photon Excited
Photoluminescence and Lasing
Xin Jiang Feng,[a] Po Lam Wu,[b] Hoi Lam Tam,[b] King Fai Li,[b] Man Shing Wong,*[a] and
Kok Wai Cheah*[b]
Abstract: A novel series of diphenyl-
amino- and 1,2,4-triazole-end-capped,
these materials. Although the absorp-
tion and emission maxima of the highly
fluorescent and extended oligofluo-
easily be modified or tuned by an in-
corporation of thienyl unit(s) into the
fluorene-based p-conjugated core with
which exceptionally large three-photon
absorption cross sections up to 3.59ꢀ
10ꢀ77 cm6 s2 in the femtosecond regime
have been obtained, thereby highlight-
ing the potential of this series of pho-
tonic materials. The optimized full
width at half-maximum of the cavity-
less three-photon upconverted blue
lasing spectra are sharply narrowed to
approximately 6 nm with an efficiency
of up to 0.013%.
ACHTUNGTRENNUNG
fluorene-based, p-conjugated oligomers
that includes extended oligofluorenes
and oligothienylfluorenes has been syn-
thesized by means of the palladium-
catalyzed Suzuki cross-coupling of 9,9-
dibutyl-7-(diphenylamino)-2-fluorenyl-
boronic acid and the corresponding
1,2,4,-triazole-based aryl halide as a
key step. It was demonstrated that effi-
cient two- and three-photon excited
photoluminescence and lasing in the
blue region are obtained by pumping
near-infrared femtosecond lasers on
AHCTUNGTRENNrGUN enes reach a saturation limit, there
exists an effective conjugation length
for an optimum three-photon absorp-
tion cross section in the homologous
oligofluorene series. On the other
hand, the multiphoton excited emission
spectrum and lasing wavelength can
Keywords: absorption
·
laser
chemistry · luminescence · oligo-
fluorenes · photochemistry
Introduction
absorption process, multiphoton absorption offers many ad-
vantages for the technological applications of high-capacity
data storage,[1] three-dimensional microfabrication,[2] biologi-
cal imaging,[3] photodynamic therapy,[4] and frequency-up-
converted lasing.[5] Three-photon absorption may be more
advantageous than two-photon absorption because of the
use of a longer excitation wavelength and the cubic depend-
ence of the input light intensity, which give rise to a better
spatial confinement of the excitation volume. In contrast to
the tremendous effort spent on the investigation of two-
photon-absorption properties over the past decades, there
have been only a few studies on the structure–property rela-
tionships for three-photon-absorption.[6] In principle, donor–
acceptor chromophores possessing a highly polarizable p-
conjugated system are highly two-photon-absorption active;
however, it is not guaranteed that they will exhibit an inter-
esting and useful three-photon-absorption property and can
be used for applications such as frequency-upconverted
lasing. To exhibit multiphoton-absorption upconverted
lasing, molecules are required to possess high-fluorescence
quantum efficiency, a significant multiphoton absorption
cross section, and low fluorescent reabsorption, which could
affect the lasing threshold and the attainment of optical
Multiphoton absorption, mainly two-photon and three-
photon absorption, has drawn considerable interest over the
years due to its potential applications in various optoelec-
tronics and photonics capacities. Owing to the use of the
long-wavelength/low-energy excitation source and the char-
acteristics of the intensity dependence of the multiphoton
[a] X. J. Feng, Prof. M. S. Wong
Department of Chemistry and Centre for Advanced
Luminescence Materials
Hong Kong Baptist University, Kowloon Tong
Hong Kong SAR (China)
Fax : (+852)34117348
E-mail: mswong@hkbu.edu.hk
[b] P. L. Wu, Dr. H. L. Tam, Dr. K. F. Li, Prof. K. W. Cheah
Department of Physics and Centre for Advanced
Luminescence Materials
Hong Kong Baptist University, Kowloon Tong
Hong Kong SAR (China)
Fax : (+852)34115813
E-mail: kwcheah@hkbu.edu.hk
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gain. As a result, only a few multiphoton-excited (and in
particular, three-photon-excited) fluorescent molecules can
exhibit frequency-upconverted lasing.[5]
thienylfluorene-derived oligomers exhibit remarkably large
three-photon-absorption cross sections up to 3.59ꢀ
10ꢀ77 cm6 s2 at 1270 nm, which is the highest value measured
in the femtosecond regime so far. In addition, the highest
cavityless three-photon-upconverted blue-lasing efficiency of
0.013% was achieved by using p-Ph2N-OF(5)-TAZ.
Because of their excellent chemical, thermal, and photo-
chemical stabilities, as well as the ease of structural tuning
to adjust their electronic and morphological properties, fluo-
rene-based functional molecules/materials constituting one
of the important classes of p-conjugated molecular materials
have recently drawn considerable attention for their poten-
tial applications in optoelectronic devices, particularly for
blue-emitting organic light emitting diodes (OLED).[7] Elec-
tron-deficient triazole (TAZ) derivatives have been found
useful as a thermally stable and efficient electron-transport-
ing and hole-blocking material in OLEDs;[8] however, their
potential use as a photonic material has been rarely ex-
plored. On account of its electron-deficient nature, the tria-
zole moiety could play the functional role in an electron-ac-
cepting group when coupled with a strong electron donor,
that is, a diphenylamino group, thereby giving rise to a
donor–acceptor chromophore.
Results and Discussion
Synthesis: The previously developed convergent approach[7e]
was used to synthesize the highly extended, asymmetrically
disubstituted diphenylamino- and 1,2,4-triazole-end-capped,
fluorene-based, p-conjugated oligomers that include penta-
fluorene and sexifluorene (p-Ph2N-OF(n)-TAZ, in which
n=5 and 6, respectively), and oligothienylfluorenes (p-
Ph2N-OF(n)OT(m)-TAZ). The synthetic routes to these
compounds are outlined in Schemes 1 and 2. Palladium-cata-
lyzed Suzuki cross-coupling of 9,9-dibutyl-7-(diphenyl-
We have recently demonstrated efficient multiphoton-ex-
cited deep blue photoluminescence and lasing on a homolo-
gous series of diphenylamino- and 1,2,4-triazole-end-capped,
p-conjugated oligofluorenes (OFs), p-Ph2N-OF(n)-TAZ (n=
2–4), in which the multiphoton-excited emission and lasing
wavelengths are independent of the oligofluorenyl length.
However, the three-photon absorption cross section and the
lasing efficiency increase with a change in the oligofluorenyl
unit from bifluorene to quarterfluorene.[9] To continue our
investigation on the structure–multiphoton-absorption prop-
erty correlations of functional materials including upcon-
verted emission properties, the multiphoton absorption cross
section, wavelength dependence of the three-photon-absorp-
tion cross section, and upconverted lasing properties, we
report herein the synthesis and structure–multiphoton-ab-
sorption property relationships of a new series of fluorene-
based p-conjugated oligomers including pentafluorene, sexi-
fluorene (p-Ph2N-OF(n)-TAZ, in which n=5 and 6, respec-
tively), and oligothienylfluorenes, p-Ph2N-OF(n)OT(m)-
TAZ, asymmetrically disubstituted with diphenylamino and
1,2,4-triazole end-caps.
ACHTUNGTRENaNUGN mino)-2-fluorenylboronic acid (5) and the corresponding
1,2,4-triazole-based aryl halide was employed as a key step
to synthesize the target oligomers.
Palladium-catalyzed Suzuki cross-coupling of triazole-sub-
stituted terfluorene iodide 1a and trimethylsilylfluorenylbor-
onic acid 2 by using PdACHTNUGRTENNUG(OAc)2/2PACHTUGNTREN(NUNG o-tolyl)3 as a catalyst af-
forded triazole-substituted trimethylsilylquaterfluorene 3a
in excellent yield (93%). Iododesilylation of 3a was per-
formed in the presence of silver trifluoroacetate at 808C,
thereby giving the corresponding iodide 4a in 94% yield.
Suzuki cross-coupling of iodide 4a and boronic acid 5 gave
the desired p-Ph2N-OF(5)-TAZ in 80% yield. Following a
similar reaction sequence for the preparation of the inter-
mediates, the higher homologue p-Ph2N-OF(6)-TAZ was
readily synthesized by the cross-coupling of boronic acid 5
and iodide 4b in 80% yield.
Palladium-catalyzed Suzuki cross-coupling of the bromide
6 and 2-thienylboronic acid 7 yielded the 1,2,4-triazole de-
rivative 8 in 82% yield. Bromination of 8 with N-bromosuc-
cinimide (NBS) in CHCl3 heated at reflux gave bromide 9
in 87% yield. Suzuki cross-coupling bromide 9 and boronic
acid 5 afforded p-Ph2N-OFOT-TAZ in 82% yield. In a simi-
lar fashion, the cross-coupling of triazole-substituted fluo-
rene iodide 10 and boronic acid 7 gave triazole-substituted
fluorenylthiophene 11 in an excellent yield. NBS bromina-
tion of 11 afforded the corresponding bromide 12 in a quan-
titative yield. Suzuki cross-coupling of 11 and 5 afforded p-
Ph2N-OFOTOF-TAZ in a moderate yield. On the other
hand, palladium-catalyzed Kumada cross-coupling of bro-
mide 12 and the freshly prepared thienylmagnesium bro-
mide in THF afforded triazole-substituted fluorenylbithio-
phene 13, which was iodinated by N-iodosuccinimide (NIS),
thereby giving the corresponding iodide 14 in 89% yield.
Suzuki cross-coupling of 14 and 5 gave the desired p-Ph2N-
OFOT(2)OF-TAZ in 68% yield. All the newly synthesized,
asymmetrically disubstituted dipolar oligofluorenes were
fully characterized with 1H and 13C NMR spectroscopy,
In this contribution, we have demonstrated that the multi-
photon-excited emission spectrum and lasing wavelength
can easily be modified or tuned by an incorporation of
thienyl unit(s) into a fluorene-based, p-conjugated core with
diphenylamino and 1,2,4-triazole end-caps. Importantly,
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Fluorene-Based p-Conjugated Oligomers
FULL PAPER
Scheme 1. Synthesis of asymmetrically disubstituted diphenylamine and 1,2,4-triazole pentafluorene (p-Ph2N-OF(5)-TAZ) and sexifluorene
(p-Ph2N-OF(6)-TAZ).
MALDI-TOF HRMS, and elemental analysis, and were
found to be in good agreement with their structures. The
thermal properties of the newly synthesized oligomers were
examined by thermogravimetric analysis (TGA) under ni-
trogen. All the oligomers showed very high thermal stabili-
ties with decomposition temperatures (Td) greater than
4508C, which is a prerequisite for high-energy laser pump-
ing.
Linear optical properties: The linear and nonlinear optical
properties of the newly synthesized donor–acceptor oligo-
mers measured in toluene are summarized in Table 1. All
these fluorene-based oligomers show very similar spectral
features, which are composed of two major absorption
bands. The weak absorption peak appears around 300–
310 nm and is attributed to the n!p* transition of triaryla-
mine moieties, and the broad absorption band spanning
Table 1. Summary of linear optical measurements of p-Ph2N-OF(n)-TAZ and p-Ph2N-OF(n)OT(m)-TAZ in various solvents and their thermal
properties.
abs
max
em [a]
max
[a,b]
abs [c]
max
em [c]
max
[b,c]
abs [d]
max
em [d]
max
[b,d]
[e]
l
[a] [nm]
l
FFL
l
[nm]
l
FFL
l
[nm]
l
FFL
Tdec
(e [ꢀ104 mꢀ1 cmꢀ1])
[nm]
(e [ꢀ104 mꢀ1 cmꢀ1])
[nm]
(e [ꢀ104 mꢀ1 cmꢀ1])
[nm]
[8C]
p-Ph2N-OF(5)-TAZ
p-Ph2N-OF(6)-TAZ
p-Ph2N-OFOT-TAZ
p-Ph2N-OFOTOF-TAZ
p-Ph2N-OFOT(2)OF-TAZ
378 (18.66)
379 (22.02)
397 (6.16)
403 (8.43)
415 (6.89)
421
420
452
454
483
0.95
379 (19.30)
380 (23.40)
398 (5.82)
403 (8.34)
416 (7.79)
436
435
487
471
488
0.86
384 (20.55)
385 (21.92)
397 (6.00)
406 (9.08)
418 (7.53)
470
470
538
506
523
0.80
460
456
508
450
488
0.99
0.61
0.67
0.40
0.86
0.54
0.61
0.37
0.82
0.63
0.64
0.34
[a] Measured in toluene (ꢁ10ꢀ5 m). [b] Using quinine sulfate monohydrate (F350 =0.58) as a standard. [c] Measured in CHCl3 (ꢁ10ꢀ5 m). [d] Measured in
DMF (ca. 10ꢀ5 m). [e] Determined by using a thermal gravimetric analyzer with a heating rate of 108Cminꢀ1 under N2.
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M. S. Wong, K. W. Cheah et al.
Scheme 2. Synthesis of asymmetrically disubstituted diphenylamine and 1,2,4-triazole oligothienylfluorenes, p-Ph2N-OF(n)OT(m)-TAZ.
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Fluorene-Based p-Conjugated Oligomers
FULL PAPER
from 378–415 nm corresponds to the p!p* transition of the
fluorene-based p-conjugated core (Figure 1). In general, the
absorption spectra of these donor–acceptor fluorene-based
Figure 2. Absorption (a) and fluorescence (b) spectra of p-Ph2N-OF(n)-
TAZ and p-Ph2N-OF(n)OT(m)-TAZ in DMF.
Upon replacing the fluorenyl with the thienyl ring(s) in
the p-conjugated core, the absorption and fluorescence spec-
tra of p-Ph2N-OF(n)OT(m)-TAZ redshift substantially with
Dlmax in the range of 20–65 nm relative to those of the cor-
responding p-Ph2N-OF(n)-TAZ (e.g., p-Ph2N-OFOT-TAZ:
Figure 1. Absorption (a) and fluorescence (b) spectra of p-Ph2N-OF(n)-
TAZ and p-Ph2N-OF(n)OT(m)-TAZ in toluene.
abs
em
oligomers do not show a significant solvatochromic effect.
In contrast, the fluorescence spectra are solvent dependent,
which is to say the spectra become structureless and exhibit
large redshifts (40–70 nm) with an increase in solvent polari-
ty (Figure 2). This indicates the dipolar or charge-transfer
character of these oligomers in the first excited states.
Furthermore, as seen from the absorption and fluores-
cence spectra of the homologous oligofluorene series p-
Ph2N-OF(n)-TAZ, in which n=2–6 in different solvents, the
molar absorptivity continues to increase and the fluores-
cence quantum yield (FFL) remains very high with an exten-
sion of the oligomeric length; however, the absorption and
emission maxima show a trend of saturation for the newly
synthesized pentafluorene and sexifluorene, thereby indicat-
ing that the effective conjugation length for the optical gap
is reached in this end-capped oligofluorene series. On the
other hand, the fluorescence quantum yields of the series
generally decrease concomitantly with an increase in the sol-
vent polarity.
l
=397 nm and
l
=452 nm vs. p-Ph2N-OF(2)-TAZ:
max
max
abs
l
x =375 nm and lemmax =424 nm in toluene). Although the
max
fluorescence quantum yields of this p-Ph2N-OF(n)OT(m)-
TAZ series are scarcely affected by various solvents, they
are significantly smaller (40–67%) than the corresponding
p-Ph2N-OF(n)-TAZ series (86–89%), which is attributable
to the increased nonradiative decay through intersystem
crossing caused by the heavy-atom effect of sulfur.[10]
Multiphoton-absorption properties: The multiphoton-ab-
sorption photoluminescence and lasing properties were in-
vestigated by using a femtosecond pulsed laser as an excita-
tion source. The results of the multiphoton-absorption mea-
AHCTUNGTREGsNNNU urements are tabulated in Table 2. The newly synthesized
donor–acceptor fluorene-based, p-conjugated oligomers
show not only two-photon-induced photoluminescence (PL)
when excited at 800 nm but also strong three-photon-upcon-
verted PL when excited at 1.3 mm. The two-photon- and
three-photon-upconverted PL spectral characteristics are
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M. S. Wong, K. W. Cheah et al.
Table 2. Summary of nonlinear optical measurements of p-Ph2N-OF(n)-TAZ and p-Ph2N-OF(n)OT(m)-TAZ.
em [a,b]
max
[a,b]
em [a,c]
max
[a,c,d]
[a,c]
2PA l
2PA llasing
3PA l
s3
[cm6 s2]
3PA llasing
3PA lasing ef-
ficiency[a,c] [%]
[nm]
[nm]
[nm]
N
[nm]
p-Ph2N-OF(5)-TAZ
p-Ph2N-OF(6)-TAZ[e]
p-Ph2N-OFOT-TAZ
p-Ph2N-OFOTOF-TAZ
p-Ph2N-OFOT(2)-TAZ
447
449
488
489
520
447
452
484
–
449
452
488
487
520
5.27ꢀ10ꢀ79
445
448
482
–
0.013
–
0.0013
–
–
1.38ꢀ10ꢀ79[f]
9.66ꢀ10ꢀ78
2.35ꢀ10ꢀ78
2.03ꢀ10ꢀ78
–
–
[a] Measured in toluene using 10ꢀ2 m. [b] Excited at 800 nm femtosecond laser pulses [c] Excited at 1.34 mm femtosecond laser pulses. [d] Determined by
using an optical limiting method using femtosecond laser pulses. [e] Measured using 5ꢀ10ꢀ3 m. [f] Determined by a comparative method using p-Ph2N-
OF(5)-TAZ as a
standard.
very similar to those of one-photon excited counterparts
(Figure 3), thereby suggesting that their emission states
should be the same. Compared with the one-photon emis-
sion spectra, the two- and three-photon excited fluorescence
spectra consistently show a small redshift at high concentra-
tion likely due to the reabsorption effect. To determine the
three-photon-absorption cross sections (s3), an optical limit-
ing method[6d] using 1.34 mm-femtosecond laser pulses in tol-
uene (10ꢀ2 m) were carried out. Interestingly, the extended
oligofluorenes p-Ph2N-OF(5)-TAZ and p-Ph2N-OF(6)-TAZ
show a progressive decrease in s3, with values of 5.27ꢀ10ꢀ79
and 1.38ꢀ10ꢀ79 cm6 sꢀ2, respectively, relative to that of their
lower homologue p-Ph2N-OF(4)-TAZ
(s3=2.48ꢀ10ꢀ78 cm6 sꢀ2),[9] even though their absorption and
emission maxima reach the convergent limit. These findings
suggest that an optimal oligofluorenyl length exists for s3 in
this series. Figure 4 (left) shows the three-photon-absorption
cross-section spectra of p-Ph2N-OF(n)OT(m)-TAZ mea-
sured by comparing the fluorescence intensity excited from
1100 to 1600 nm with that of the investigated molecule ex-
cited at 1.34 mm, at which s3 was obtained by the optical
limiting method. It is important to note that upon replacing
Figure 3. Comparison of photoluminescence spectra of a) p-Ph2N-OF(5)-TAZ, b) p-Ph2N-OFOT-TAZ, c) p-Ph2N-OFOTOF-TAZ, and d) p-Ph2N-
OFOT(2)OF-TAZ excited by two- and three-photon excitation in toluene. One of the photoluminescence spectra is offset for clarity.
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Fluorene-Based p-Conjugated Oligomers
FULL PAPER
rectly gives the experimental evidence of a three-photon ex-
citation process.
Upon pumping femtosecond laser pulses at 800 nm, p-
Ph2N-OF(n)-TAZ (n=5 and 6) exhibit remarkable two-
photon-upconverted blue lasing. The two-photon-excited
lasing spectra of these extended oligofluorenes were very
similar in which the lasing spectra are significantly narrowed
(FWHMꢁ12 nm), even though such an upconversion at
800 nm is not an optimum condition for the two-photon-ex-
cited process. Interestingly, p-Ph2N-OFOT-TAZ also exhibits
spectral narrowing (FWHM=17 nm) and lasing upon pump-
ing at 800 nm; however, the other oligothienylfluorenes, p-
PhN-OFOTOF-TAZ and p-PhN-OFOT(2)OF-TAZ, only
show two-photon-excited photoluminescence, which is at-
tributed to their decreased fluorescence quantum yields.
Consistently, p-Ph2N-OF(5)-TAZ, p-Ph2N-OF(6)-TAZ,
and p-Ph2N-OFOT-TAZ also exhibit remarkable three-
photon-upconverted blue lasing with peaks at 445, 449, and
482 nm, respectively, upon pumping femtosecond laser
pulses at 1.34 mm. Figure 5 shows the plot of the full width
Figure 4. a) Three-photon-absorption cross-section spectra of p-Ph2N-
OF(5)-TAZ and p-Ph2N-OF(n)OF(m)-TAZ measured by using a compa-
rative method. b) Logarithmic plots of the power dependence of relative
three-photon-induced fluorescence on pulse intensity using an infrared
femtosecond laser as the exciting source for p-Ph2N-OF(5)-TAZ and p-
Ph2N-OF(n)OT(m)-TAZ.
Figure 5. Plots of full width at half-maximum (FWHM) of emission spec-
tra of p-Ph2N-OFOT-TAZ versus excitation wavelength.
fluorenyl unit(s) with thienyl unit(s) into a p-conjugated
core, s3 is substantially enhanced relative to the correspond-
ing oligofluorene counterparts (Table 2), with s3 values up
to 3.59ꢀ10ꢀ77 cm6 s2 at 1270 nm for p-Ph2N-OFOT-TAZ
(Figure 4, left), which is the highest value ever measured in
the femtosecond regime. These results also suggest that the
thienyl moiety is a useful and effective structure unit to en-
hance the three-photon-absorption cross section. The in-
creased nonlinearity is attributed to the enhanced electron
delocalization and intramolecular charge transfer of an
entire thiophene-incorporated p-conjugated system relative
to that of the corresponding oligofluorene, which is consis-
tent with the redshift of the absorption and emission spec-
tra. This also provides a means to tune the three-photon-ex-
cited emission wavelengths and cross sections of the oligo-
mers. The power-cubic dependence of three-photon-excited
at half-maximum (FWHM) of three-photon-upconverted PL
and lasing spectra with various excitation wavelengths for p-
Ph2N-OFOT-TAZ. As shown in Figure 6, the three-photon-
upconversion lasing spectra of p-Ph2N-OF(5)-TAZ, p-Ph2N-
OF(6)-TAZ, and p-Ph2N-OFOT-TAZ are sharply narrowed
relative to their respective PL spectra. The optimized
FWHM of the lasing spectra is 5.5 nm for p-Ph2N-OF(5)-
TAZ, 6.5 nm for p-Ph2N-OF(6)-TAZ, and 6.2 nm for p-
Ph2N-OFOT-TAZ. Figure 7 shows the plot of the output
versus input power relation for p-Ph2N-OF(5)-TAZ, thereby
clearly indicating the lasing threshold behavior. Despite the
smaller three-photon-absorption cross-sections for p-Ph2N-
OF(5)-TAZ, its three-photon-upconverted cavityless lasing
efficiency is still very high, thus making it as efficient as that
of p-Ph2N-OF(4)-TAZ.[9] Because of its poor solubility and
photostability, the lasing efficiency of p-Ph2N-OF(6)-TAZ
could not be determined. On the other hand, p-Ph2N-
OFOT-TAZ showed rather low three-photon-upconverted
fluorescence
for
p-Ph2N-OF(5)-TAZ
and
p-Ph2N-
OF(n)OT(m)-TAZ at 1.3 or 1.5 mm has a gradient in the
range of 2.97–3.14, as shown in Figure 4 (right), which di-
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M. S. Wong, K. W. Cheah et al.
Figure 7. Plots of output power versus input pump power for the three-
photon-pumped lasing process for p-Ph2N-OF(5)-TAZ.
catalyzed Suzuki cross-coupling of 9,9-dibutyl-7-(diphenyl-
AHCTUNGTREGaNNUN mino)-2-fluorenylboronic acid and the corresponding 1,2,4-
triazole-based aryl halide as a key step. Efficient multipho-
ton-excited photoluminescence and lasing were obtained by
pumping with near-infrared femtosecond lasers. Despite the
exhibition of the saturation behavior of absorption and
emission properties/maxima in the p-Ph2N-OF(n)-TAZ
series, the highly fluorescent and extended oligofluorenes
show a decrease in the three-photon-absorption cross sec-
tion. On the other hand, the multiphoton-excited emission
spectrum and lasing wavelength can easily be modified or
tuned by an incorporation of thienyl unit(s) into the fluo-
rene-based p-conjugated core. Upon the incorporation of
thienyl unit(s), the three-photon-absorption cross section in-
creases significantly up to 3.59ꢀ10ꢀ77 cm6 s2 in the femtosec-
ond regime, thereby highlighting the promising potential of
this series. The optimized full width at half-maximum
(FWHM) of the three-photon lasing spectra of these materi-
als is sharply narrowed to approximately 6 nm. Our findings
show that the thienyl moiety is a useful and effective p-con-
jugated unit to enhance the three-photon-absorption cross
section; however, it is detrimental to upconversion lasing
applications.
Experimental Section
Figure 6. Three-photon-upconversion photoluminescence and lasing spec-
tra of p-Ph2N-OF(5)-TAZ (a) and p-Ph2N-OF(6)-TAZ (b) pumped at
1.34 mm, and p-Ph2N-OFOT-TAZ (c) pumped at 1.48 mm.
For multiphoton-excited photoluminescence and cavityless upconversion
lasing experiments, the concentration used was 1ꢀ10ꢀ2
m in toluene
except p-Ph2N-OF(6)-TAZ (5ꢀ10ꢀ3 m) because of its poor solubility. The
pump source was an optical parametric amplifier (OPA; Topas, Coher-
ent) that was pumped by a self-mode-locked Ti:sapphire laser with a
Spitfire regenerative amplifier (Spectra Physics–Tsunami; 800 nm, pulsed
width 100 fs, repetition rate 1 kHz). The laser beam passed through a po-
larizer and a focusing lens, and an IR filter (Hot Filter) was used to
block the 800 nm light. The incident laser beam was focused on the
center of the oligomer solution inside the cuvette. A second lens focused
a transmitted signal into the spectrometer (Ocean Optics, USB4000). The
same laser system was used for PL experiments. For both PL and lasing
excitation, an 800 nm lasing line directly from the Spitfire regenerative
amplifier was used, and for lasing the threshold pump power was 6 mW.
For three-photon-upconversion excitation, laser lines from the OPA
lasing efficiency, which is attributed to its reduced fluores-
cence quantum yield.
Conclusion
In summary, we have synthesized a new class of diphenyl-
ACHTUNGTRENNUNGamino- and 1,2,4-triazole-end-capped, fluorene-based, p-
conjugated oligomers, namely, p-Ph2N-OF(n)-TAZ (n=5
and 6), and p-Ph2N-OF(n)OT(m)-TAZ, by using palladium-
11688
www.chemeurj.org
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 11681 – 11691

Fluorene-Based p-Conjugated Oligomers
FULL PAPER
pumped by the Spitfire regenerative amplifier were used so that the laser
wavelength could be tuned for optimum excitation.
40.0, 34.7, 31.1, 26.0, 26.0, 25.9, 23.0, 22.9, 13.8 ppm; MS (FAB): m/z:
1860.1 [M+].
p-Ph2N-OF(5)-TAZ: The synthetic procedure for compound 3 was fol-
lowed using compound 4a (158.5 mg, 0.1 mmol), compound 5 (97.9 mg,
Compound 3a: A mixture of 1a (1.10 g, 0.84 mmol), compound 2 (0.49 g,
1.26 mmol), palladium(II) acetate (10 mg, 0.045 mmol), triACTHNUTRGNE(UNG o-tolyl)phos-
0.2 mmol), palladium(II) acetate (1.2 mg, 0.005 mmol), triACTHNUTRGNE(UNG o-tolyl)phos-
phine (28 mg, 0.092 mmol), 2m K2CO3 (2 mL), toluene (25 mL), and
methanol (10 mL) under a nitrogen atmosphere was heated at 758C over-
night with good magnetic stirring. After cooling to room temperature,
the reaction mixture was poured into water and extracted with ethyl ace-
tate (30 mL) followed by dichloromethane (30 mL). The combined or-
ganic layer was dried over anhydrous Na2SO4, evaporated to dryness, and
the residue was purified by silica gel column chromatography using 8:1
dichloromethane/ethyl acetate as eluent, thereby affording 3a (1.20 g,
93%) as a white solid. 1H NMR (400 MHz, CDCl3, 258C): d=7.76–7.83
(m, 7H), 7.46–7.73 (m, 24H), 7.36–7.38 (m, 2H), 7.30 (d, J=6.4 Hz, 2H),
7.25 (d, J=7.2 Hz, 2H), 2.04–2.10 (m, 16H), 1.28 (s, 9H), 1.09–1.18 (m,
16H), 0.68–0.79 (m, 40H), 0.33 ppm (s, 9H); 13C NMR (100 MHz,
CDCl3, 258C): d=154.8, 154.4, 152.7, 151.7, 151.6, 150.1, 142.5, 141.3,
140.6, 140.4, 140.3, 140.0, 139.9, 139.7, 139.0, 138.7, 135.5, 131.8, 130.0,
129.6, 129.0, 128.3, 128.0, 127.5, 126.9, 126.0, 125.6, 125.3, 123.9, 121.4,
121.2, 120.0, 119.9, 118.9, 55.2, 55.0, 40.2, 39.9, 34.7, 31.1, 26.1, 26.0, 23.0,
23.0, 13.8, 13.7, ꢀ0.8 ppm; MS (FAB): m/z: 1530.2 [M+].
phine (3.1 mg, 0.01 mmol), 2mK2CO3 (1 mL), toluene (10 mL), and meth-
anol (4 mL). The crude product was purified by silica gel column chroma-
tography using 8:1 dichloromethane/ethyl acetate as an eluent, thereby
affording p-Ph2N-OF(5)-TAZ (153 mg, 80%) as a light yellow solid.
1H NMR (400 MHz, CDCl3, 258C): d=7.77–7.85 (m, 8H), 7.49–7.72 (m,
27H), 7.38 (d, J=8.4 Hz, 2H), 7.31 (d, J=8.4 Hz, 2H), 7.24–7.32 (m,
4H), 7.15 (d, J=8.0 Hz, 5H), 7.00–7.06 (m, 3H), 1.90–2.37 (m, 20H),
1.29 (s, 9H), 1.03–1.19 (m, 20H), 0.68–0.80 ppm (m, 50H); 13C NMR
(100 MHz, CDCl3, 258C): d=154.8, 154.4, 152.8, 152.3, 151.7, 151.4,
147.9, 147.1, 142.5, 140.6, 140.6, 140.4, 140.1, 140.0, 139.9, 139.8, 139.7,
139.5, 138.7, 135.9, 135.5, 130.0, 129.6, 129.1, 129.0, 128.3, 128.0, 126.9,
126.0, 125.6, 125.3, 123.9, 123.8, 123.4, 122.4, 121.4, 121.2, 121.1, 120.3,
120.0, 119.9, 119.3, 55.2, 55.0, 40.2, 39.9, 34.7, 31.1, 26.0, 23.0, 23.0, 13.8,
13.8 ppm; HRMS (MALDI-TOF): m/z: 1903.2173 [M++H]; elemental
analysis calcd (%) for C141H152N4: C 89.00, H 8.05, N 2.94; found: C
88.97, H 7.76, N 2.94.
p-Ph2N-OF(6)-TAZ: The synthetic procedure for compound 3 was fol-
lowed using compound 4b (531 mg, 0.29 mmol), compound 5 (279 mg,
0.57 mmol), palladium(II) acetate (3.2 mg, 0.014 mmol), triACTHNUTRGNE(UNG o-tolyl)phos-
Compound 3b: The synthetic procedure for compound 3a was followed
using compound 1b (158.5 mg, 0.1 mmol), compound
2
(58.3 mg,
0.15 mmol), palladium(II) acetate (1.1 mg, 0.005 mmol), triAHCTUNGRETG(NNUN o-tolyl)phos-
phine (8.7 mg, 0.029 mmol), 2mK2CO3 (1.5 mL), toluene (20 mL), and
methanol (8 mL). The crude product was purified by silica gel column
chromatography using 8:1 dichloromethane/ethyl acetate as an eluent,
thereby affording 530 mg (80%) of a yellow solid. 1H NMR (400 MHz,
CDCl3, 258C): d=7.76–7.84 (m, 10H), 7.47–7.70 (m, 33H), 7.35 (d, J=
8.8 Hz, 2H), 7.29 (d, J=8.4 Hz, 2H), 7.22–7.24 (m, 2H), 2.13 (m, 6H),
6.98–7.04 (m, 4H), 2.09 (m, 24H), 1.27 (s, 9H), 1.01–1.14 (m, 24H), 0.66–
0.78 ppm (m, 60H); 13C NMR (100 MHz, CDCl3, 258C): d=154.8, 154.4,
152.8, 152.3, 151.8, 151.4, 147.9, 147.1, 142.5, 140.6, 140.4, 140.1, 140.0,
139.8, 139.7, 139.5, 138.7, 135.9, 135.5, 130.0, 129.6, 129.1, 129.0, 128.3,
128.0, 126.9, 126.1, 125.6, 125.4, 123.9, 123.8, 123.4, 122.4, 121.4, 120.3,
120.0, 119.9, 119.3, 55.2, 55.0, 40.2, 40.0, 34.7, 31.1, 26.1, 23.1, 23.0, 13.8,
13.8 ppm; HRMS (MALDI-TOF): m/z: 2179.4032 [M++H]; elemental
analysis calcd (%) for C162H176N4: C 89.29, H 8.14, N 2.57; found: C
89.55, H 8.13, N 2.56.
phine (3.2 mg, 0.01 mmol), 2m K2CO3 (1 mL), toluene (10 mL), and
methanol (4 mL). The crude product was purified by silica gel column
chromatography using 8:1 dichloromethane/ethyl acetate as an eluent,
thereby affording 3b (153 mg, 80%) as a light yellow solid. 1H NMR
(400 MHz, CDCl3, 258C): d=7.77–7.85 (m, 8H), 7.46–7.74 (m, 29H),
7.38 (d, J=8.4 Hz, 2H), 7.32 (d, J=8.8 Hz, 2H), 7.24–7.27 (m, 2H), 2.03–
2.09 (m, 20H), 1.27 (s, 9H), 1.08–1.18 (m, 20H), 0.66–0.78 (m, 50H),
0.31 ppm (s, 9H); 13C NMR (100 MHz, CDCl3, 258C): d=154.8, 154.4,
152.8, 151.7, 151.7, 151.6, 150.1, 142.5, 141.3, 140.6, 140.6, 140.4, 140.3,
140.3, 140.0, 140.0, 139.9, 139.7, 139.0, 138.7, 135.5, 131.8, 130.0, 129.6,
129.0, 128.3, 127.9, 127.5, 126.9, 126.0, 125.9, 125.6, 125.3, 123.9, 121.4,
121.2, 120.0, 119.9, 118.9, 55.2, 55.0, 40.2, 39.9, 34.7, 31.1, 26.1, 26.0, 23.0,
23.0, 23.0, 13.8, 13.7, ꢀ0.86 ppm; MS (FAB): m/z: 1806.3 [M+].
Compound 4a: A mixture of 3a (1.09 g, 0.71 mmol), silver trifluoroace-
tate (0.24 g, 1.1 mmol), and iodine (0.22 g, 0.85 mmol) in chloroform
(30 mL) was heated to reflux and stirred for 4 h. After cooling to room
temperature, the mixture was poured into sodium sulfite solution and ex-
tracted with dichloromethane (3ꢀ30 mL). The combined organic layer
was dried over anhydrous Na2SO4 and evaporated to dryness. The crude
product was purified by short silica gel column chromatography using 8:1
dichloromethane/ethyl acetate as eluent, thereby affording the iodide 4a
as a light yellow solid (1.06 g, 94%). 1H NMR (400 MHz, CDCl3, 258C):
d=7.81–7.84 (m, 9H), 7.45–7.71 (m, 24H), 7.37 (d, J=8.8, 2H), 7.30 (d,
J=8.8, 2H), 7.23–7.25 (m, 2H), 1.95–2.13 (m, 16H), 1.28 (s, 9H), 1.07–
1.18 (m, 16H), 0.65–0.78 ppm (m, 40H); 13C NMR (100 MHz, CDCl3,
258C): d=154.8, 154.4, 153.4, 152.8, 150.8, 142.5, 141.0, 140.6, 140.6,
140.4, 140.3, 140.3, 140.1, 140.0, 139.9, 139.9, 139.7, 139.2, 138.7, 135.8,
135.5, 132.0, 130.0, 129.6, 129.0, 128.3, 128.0, 126.9, 126.1, 126.1, 125.6,
125.3, 123.9, 121.4, 121.2, 120.0, 119.9, 92.4, 55.3, 55.2, 40.2, 40.0, 34.7,
31.1, 26.0, 26.0, 25.9, 23.0, 23.0, 13.8 ppm; MS (FAB): m/z: 1583.9 [M+].
Compound 8: The synthetic procedure for compound 3 was followed
using compound 6 (609 mg, 1.41 mmol), 2-thiopheneboronic acid (7;
360 mg, 2.81 mmol), palladium(II) acetate (11 mg), triACTHNUGRTENUNG(o-tolyl)phosphine
(26 mg), toluene (15 mL), methanol (6 mL), and 2mK2CO3 (2 mL). The
crude product was purified by silica gel column chromatography using
8:1 dichloromethane/ethyl acetate as an eluent, thereby affording
8
(468 mg, 82%) as a yellow solid. 1H NMR (400 MHz, CDCl3, 258C): d=
7.05–7.50 (m, 16H), 1.28 ppm (s, 9H); 13C NMR (67 MHz, CDCl3, 258C):
d=154.6, 154.0, 143.0, 135.1, 129.8, 129.5, 128.9, 128.1, 128.0, 127.7, 125.6,
125.4, 125.2, 123.7, 123.6, 117.6, 34.7, 31.1 ppm; MS (FAB): m/z: 435.9
[M+].
Compound 9: A mixture of compound 8 (271 mg, 0.62 mmol) and NBS
(133 mg, 0.75 mmol) in chloroform was heated at reflux overnight. The
reaction mixture washed with brine, dried over anhydrous sodium sulfate,
and evaporated in vacuum. The residue was purified by silica gel column
chromatography using 8:1 dichloromethane/ethyl acetate as an eluent,
1
Compound 4b: The iodo-desilylation procedure for compound 4a was
followed using compound 3b (547 mg, 0.30 mmol), iodine (92 mg,
0.36 mmol), silver trifluoroacetate (100 mg, 0.45 mmol), and chloroform
(20 mL). The crude product was purified by silica gel column chromatog-
raphy using 8:1 dichloromethane/ethyl acetate as an eluent, thereby af-
fording 4b (530 mg, 85%) as a yellow solid. 1H NMR (400 MHz, CDCl3,
258C): d=7.75–7.84 (m, 9H), 7.48–7.71 (m, 28H), 7.37 (d, J=8.4 Hz,
2H), 7.30 (d, J=8.4 Hz, 2H), 7.25 (d, J=7.6 Hz, 2H), 2.03–2.11 (m,
20H), 1.28 (s, 9H), 1.09–1.17 (m, 20H), 0.68–0.80 ppm (m, 50H);
13C NMR (100 MHz, CDCl3, 258C): d=154.8, 154.4, 153.3, 152.7, 150.8,
142.5, 141.0, 140.6, 140.5, 140.3, 140.1, 139.9, 139.9, 139.7, 139.2, 138.7,
135.8, 135.5, 132.0, 130.0, 129.6, 129.0, 128.3, 127.9, 126.9, 126.1, 126.0,
125.6, 125.3, 123.9, 121.4, 121.2, 121.2, 120.0, 119.9, 92.4, 55.3, 55.2, 40.1,
thereby affording 9 (468 mg, 87%) as a yellow solid. H NMR (400 MHz,
CDCl3, 258C): d=7.02–7.49 (m, 15H), 1.28 ppm (s, 9H); 13C NMR
(67 MHz, CDCl3, 258C): d=154.6, 153.8, 152.6, 144.3, 135.1, 134.2, 130.8,
129.8, 129.5, 128.9, 128.1, 127.7, 126.0, 125.2, 125.0, 123.7, 123.6, 112.1,
34.7, 31.0 ppm; MS (FAB): m/z: 516.1 [M+].
p-Ph2N-OFOT-TAZ: The synthetic procedure for compound 3 was fol-
lowed using compound 9 (400 mg, 0.78 mmol), compound 5 (571 mg,
1.17 mmol), palladium(II) acetate (20 mg), triACTHNUTRGNE(NUG o-tolyl)phosphine (45 mg),
2mK2CO3 (3 mL), toluene (20 mL), and methanol (8 mL). The crude
product was purified by silica gel column chromatography using 8:1 di-
chloromethane/ethyl acetate as an eluent, thereby affording p-Ph2N-
OFOT-TAZ (560 mg, 82%) as
CDCl3, 258C): d=7.34–7.61 (m, 16H), 7.23–7.27 (m, 7H), 7.11–7.14 (m,
a
yellow solid. 1H NMR (400 MHz,
Chem. Eur. J. 2009, 15, 11681 – 11691
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
11689

M. S. Wong, K. W. Cheah et al.
5H), 6.99–7.03 (m, 3H), 1.85–1.92 (m, 4H), 1.29 (s, 9H), 1.03–1.18 (m,
4H), 0.66–0.72 ppm (m, 10H); 13C NMR (100 MHz, CDCl3, 258C): d=
154.8, 154.2, 152.7, 152.2, 151.4, 147.8, 147.2, 145.3, 140.7, 135.5, 135.3,
135.2, 130.0, 129.6, 129.1, 129.0, 127.9, 125.9, 125.5, 125.3, 125.1, 124.7,
123.8, 123.6, 123.3, 122.5, 120.3, 119.6, 119.4, 119.0, 54.9, 39.9, 34.6, 31.0,
25.9, 22.9, 13.8 ppm; HRMS (MALDI-TOF): m/z: 878.4379 [M+]; ele-
mental analysis calcd (%) for C61H58N4S: C 83.33, H 6.65, N 6.37; found:
C 83.12, H 6.60, N 6.32.
7.17 (d, J=3.6, 1H), 7.02–7.04 (t, J=4.4, 1H), 2.0–2.05 (m, 4H), 1.28 (s,
9H), 1.04–1.13 (m, 4H), 0.61–0.68 ppm (m, 10H); 13C NMR (100 MHz,
CDCl3, 258C): d=154.8, 154.3, 152.7, 151.7, 151.6, 143.7, 142.3, 140.3,
140.2, 138.8, 137.4, 136.4, 135.4, 132.9, 129.9, 129.6, 129.0, 128.2, 127.9,
127.8, 126.9, 126.0, 125.6, 125.3, 124.5, 124.3, 123.9, 123.5, 121.1, 120.2,
120.0, 119.7, 55.2, 40.2, 34.6, 31.0, 25.9, 23.0, 13.7 ppm; MS (FAB): m/z:
793.2 [M+].
Compound 14: A mixture of compound 13 (488 mg, 0.61 mmol) and NIS
(180 mg, 0.80 mmol) in CHCl3 (30 mL) was heated at reflux overnight
with stirring. The crude product was purified by silica gel column chro-
matography using 8:1 dichloromethane/ethyl acetate as an eluent, there-
by affording 14 (501 mg, 89%) as a yellow solid. 1H NMR (400 MHz,
CDCl3, 258C): d=7.63–7.69 (m, 2H), 7.42–7.59 (m, 11H), 7.36–7.38 (d,
J=8.4, 2H), 7.27–7.30 (m, 3H), 7.12–7.25 (m, 4H), 7.98–7.00 (m, 4H),
2.00–2.04 (m, 4H), 1.26 (s, 9H), 1.03–1.10 (m, 4H), 0.63–0.66 ppm (m,
10H); 13C NMR (100 MHz, CDCl3, 258C): d=154.6, 154.1, 152.4, 151.5,
151.3, 143.9, 143.0, 142.1, 140.1, 140.1, 140.0, 138.6, 138.6, 137.4, 137.1,
136.1, 135.2, 134.8, 132.7, 132.5, 129.8, 129.4, 128.8, 128.1, 127.7, 127.6,
126.8, 126.7, 125.8, 125.7, 125.5, 125.1, 124.8, 124.6, 124.6, 124.4, 124.1,
123.7, 123.6, 123.4, 123.3, 120.8, 120.1, 119.9, 119.4, 71.7, 55.0, 40.0, 34.4,
30.8, 25.7, 22.8, 13.6 ppm; MS (FAB): m/z: 919.5 [M+].
Compound 11: The synthetic procedure for compound 3 was followed
using compound 10 (1.50 g, 2.0 mmol), 2-thiopheneboronic acid (7;
762 mg, 6.0 mmol), palladium(II) acetate (45 mg), triACTHNUGRTENUNG(o-tolyl)phosphine
(63 mg), 2mK2CO3 (7 mL), toluene (40 mL), and methanol (15 mL). The
crude product was purified by silica gel column chromatography using
8:1 dichloromethane/ethyl acetate as an eluent, thereby affording 11
(1.24 g, 88%) as a yellow solid. 1H NMR (400 MHz, CDCl3, 258C): d=
7.68–7.73 (m, 2H), 7.59–7.62 (m, 3H), 7.486–7.56 (m, 8H), 7.37–7.39 (m,
3H), 7.25–7.32 (m, 5H), 7.09–7.12 (m, 1H), 1.99–2.02 (t, J=5.6 Hz, 4H),
1.28 (s, 9H), 1.04–1.10 (m, 4H), 0.60–0.67 ppm (m, 10H); 13C NMR
(100 MHz, CDCl3, 258C): d=154.7, 154.3, 152.6, 151.6, 151.5, 144.9,
142.3, 140.3, 140.0, 138.7, 135.3, 133.2, 129.9, 129.5, 128.9, 128.2, 127.9,
127.8, 126.8, 125.9, 125.5, 125.2, 124.8, 124.4, 123.8, 122.8, 121.0, 120.1,
119.9, 119.9, 55.1, 40.1, 34.6, 31.0, 25.8, 22.9, 13.7 ppm; MS (FAB): m/z:
711.5 [M+].
p-Ph2N-OFOT(2)OF-TAZ: The synthetic procedure for compound 3 was
followed using compound 14 (435 mg, 0.47 mmol), compound 5 (463 mg,
0.95 mmol), palladium(II) acetate (40 mg), triACTHNUTRGNE(NUG o-tolyl)phosphine (60 mg),
Compound 12: The synthetic procedure for compound 9 was followed
using compound 11 (700 mg, 0.98 mmol) and NBS (210 mg, 1.18 mmol)
in CHCl3 (30 mL). The crude product was purified by silica gel column
chromatography using 8:1 dichloromethane/ethyl acetate as an eluent,
thereby affording 778 mg of a yellow solid, which was still a mixture and
used for the coupling reaction without further purification. 1H NMR
(400 MHz, CDCl3, 258C): d=7.61–7.67 (m, 2H), 7.36–7.58 (m, 13H),
7.23–7.29 (m, 3H), 7.15–7.19 (m, 3H), 7.09 (d, J=4, 1H), 6.96–6.98 (m,
1H), 2.00–2.03 (m, 4H), 1.25 (s, 9H), 1.03–1.09 (m, 4H), 0.61–0.65 ppm
(m, 10H); 13C NMR (100 MHz, CDCl3, 258C): d=154.6, 154.1, 152.4,
151.5, 151.3, 143.9, 143.4, 143.0, 142.1, 140.1, 140.1, 140.0, 138.6, 138.6,
137.4, 137.1, 136.4, 136.1, 135.2, 134.8, 132.7, 132.5, 131.1, 129.8, 129.4,
128.8, 128.1, 127.7, 127.6, 126.7, 125.8, 125.4, 125.1, 124.8, 124.6, 124.4,
124.1, 123.7, 123.4, 123.1, 120.8, 120.1, 119.9, 119.4, 71.7, 55.0, 54.9, 40.0,
34.4, 30.8, 25.7, 22.8, 13.6 ppm; MS (FAB): m/z: 579.2 [M+].
2mK2CO3 (4 mL), toluene (30 mL), and methanol (8 mL). The crude
product was purified by silica gel column chromatography using 8:1 di-
chloromethane/ethyl acetate as an eluent, thereby affording p-Ph2N-
OFOT(2)OF-TAZ (432 mg, 68%) of a yellow solid. 1H NMR (400 MHz,
CDCl3, 258C): d=7.46–7.74 (m, 17H), 7.21–7.38 (m, 15H), 7.12–7.14 (d,
J=8.4, 2H), 6.99–7.03 (t, J=7.6, 3H), 1.86–2.05 (m, 8H), 1.28 (s, 9H),
1.05–1.12 (m, 8H), 0.66–0.73 ppm (m, 20H); 13C NMR (100 MHz, CDCl3,
258C): d=155.1, 154.6, 153.0, 152.5, 152.0, 151.9, 151.7, 148.1, 147.5,
144.2, 143.8, 142.6, 140.9, 140.6, 14.05, 139.1, 136.8, 136.4, 135.8, 135.7,
133.2, 132.2, 130.2, 129.8, 129.4, 129.3, 128.5, 128.2, 127.2, 126.3, 125.9,
125.6, 124.8, 124.7, 124.6, 124.6, 124.2, 124.1, 123.9, 123.6, 122.8, 121.4,
120.6, 120.5, 120.3, 119.9, 119.8, 119.7, 119.3, 55.4, 55.3, 40.5, 40.2, 34.9,
31.3, 26.2, 26.2, 23.2, 23.2, 14.1, 14.0 ppm; HRMS (MALDI-TOF): m/z:
1237.6248 [M++H]; elemental analysis calcd (%) for C86H84N4S2: C
83.45, H 6.84, N 4.53; found: C 83.18, H 6.69, N 4.38.
p-Ph2N-OFOTOF-TAZ: The synthetic procedure for compound 3 was
followed using compound 12 (423 mg, 0.53 mmol), compound 5 (519 mg,
1.06 mmol), palladium(II) acetate (40 mg), triACTHNUTRGNE(NUG o-tolyl)phosphine (60 mg),
2mK2CO3 (4 mL), toluene (30 mL), and methanol (8 mL). The crude
product was purified by silica gel column chromatography using 8:1 di-
chloromethane/ethyl acetate as an eluent, thereby affording p-Ph2N-
OFOTOF-TAZ (403 mg, 66%) as a yellow solid. 1H NMR (400 MHz,
CDCl3, 258C): d=7.59–7.63 (t, J=8, 2H), 7.34–7.55 (m, 15H), 7.26–7.29
(m, 4H), 7.12–7.21 (m, 8H), 7.03–7.05 (d, J=7.6, 5H), 6.89–6.94 (m,
3H), 1.75–1.97 (m, 8H), 1.29 (s, 9H), 1.06–1.16 (m, 8H), 0.67–0.76 ppm
(m, 20H); 13C NMR (100 MHz, CDCl3, 258C): d=154.8, 154.3, 152.7,
152.2, 151.7, 151.5, 151.3, 147.8, 147.1, 144.2, 143.6, 142.3, 140.5, 140.4,
140.0, 138.7, 135.6, 135.4, 133.3, 132.2, 129.9, 129.5, 129.0, 128.9, 128.2,
127.9, 126.8, 126.0, 125.6, 125.3, 124.4, 123.8, 123.8, 123.5, 123.3, 122.5,
121.0, 120.3, 120.2, 119.9, 119.6, 119.4, 119.0, 55.1, 54.9, 40.2, 39.9, 34.6,
31.0, 25.9, 25.9, 22.9, 22.9, 13.8, 13.7 ppm; HRMS (MALDI-TOF): m/z:
1154.6238 [M+]; elemental analysis calcd (%) for C82H82N4S: C 85.23, H
7.15, N 4.85; found: C 84.92, H 7.05, N 4.38.
Acknowledgements
This work is supported by the General Research Fund (GRF) of the
Hong Kong Research Grant Council (no. HKBU 202408).
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Received: June 1, 2009
Published online: September 22, 2009
Chem. Eur. J. 2009, 15, 11681 – 11691
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